Inertia for compass

Question

I am developing an application with Google Maps API v2. I have built a custom Location source to provide location Updates to the Map and also some functions to follow the user, so f.i. when the user presses the "follow" button Aggiorna[=update]BearingAuto and AggiornaPosAuto became true:

@Override
public void OnBearingChanged(float bearing) {
    if (AggiornaBearingAuto)
    {
        mMap.moveCamera(CameraUpdateFactory.newCameraPosition(CameraPosition.builder(mMap.getCameraPosition()).bearing(bearing).build()));
    }
}

@Override
public void OnLocationChanged(Location location) {
    if (AggiornaPosAuto)
    {
        CameraPosition Att = mMap.getCameraPosition();
        mMap.moveCamera(CameraUpdateFactory.newCameraPosition(
                CameraPosition.builder().bearing(Att.bearing).
                target(new LatLng(location.getLatitude(), location.getLongitude()))
                .tilt(Att.tilt).zoom(Att.zoom).build()
                ));
    }
}

and those functions update the CameraPosition, according to the values provided from my class.

Now, in that class the method which provides Bearing updates is the following:

@Override
public void onSensorChanged( SensorEvent sensorEvent ) {

    float[] inR = new float[16];
    float[] I = new float[16];
    float[] orientVals = new float[3];

    double azimuth = 0;
    double pitch = 0;
    double roll = 0;
    // Gets the value of the sensor that has been changed
    switch (sensorEvent.sensor.getType()) {  
        case Sensor.TYPE_ACCELEROMETER:
            gravity = sensorEvent.values.clone();
            break;
        case Sensor.TYPE_MAGNETIC_FIELD:
            geomag = sensorEvent.values.clone();
            break;
    }

    // If gravity and geomag have values then find rotation matrix
    if (gravity != null && geomag != null) {

        // checks that the rotation matrix is found
        boolean success = SensorManager.getRotationMatrix(inR, I, gravity, geomag);
        if (success) {
            SensorManager.getOrientation(inR, orientVals);
            azimuth = Math.toDegrees(orientVals[0]);
            pitch = Math.toDegrees(orientVals[1]);
            roll = Math.toDegrees(orientVals[2]);
        }
    }

        //finally, call OnBeraingChange in Listener
    LocListener.OnBearingChanged((float) azimuth);
}

Ok. So the problem is: the maps moves sometimes rendundantly quickly enough to get annoying, like if the Sensor is providing -4, 0, +4, 0, +6, -5, etc. continuously. This make impossible to deal with this functionality. How could Google Maps make the Map rotation so smooth and absolutely stabilized? They implemented a kind of inertia, but how?? Have someone an idea to implement such a function?

Answer 1

I have managed the problem by implementing a Kalman filter.

Answer 2

I had the same problem, you must implements a LOW PASS FILTER, because the value of magnetometer and accelerometer is more unstable. Or you must to implements one things more similar to Low pass filter Look this:Android Compass orientation on unreliable (Low pass filter)